The ability to imitate actions performed by others has long known to be deficient in autism spectrum disorders (ASD). Psychologists studying typical development have shown that imitation is a critical ability for learning complex skills-social skills in particular. The link between impaired imitation and abnormal development of social, communicative and complex motor behavior in ASD, however, is speculative and has not been documented directly. The research proposed in this application intends to look directly at the link between impaired imitation and the ability to learn new, complex skills. This knowledge is critical, as many therapies used for children with ASD rely on imitation (e.g., speech-language therapy), and the future design of better therapies depends on precise knowledge about how children with ASD learn most effectively. We examine motor skills specifically, because motor skills can be observed and quantified relatively easily. To carry out this research, we have already designed a new task in which participants learn how to perform complex gestures with their arm over a relatively short period of time. In addition to recording how well subjects with ASD (as compared with control subjects) perform these gestures, we will use EEG recordings of the brain's electrical activity to examine how motor control networks in the brain remodel themselves as individuals learn to perform the gestures more efficiently. Data from adult and pediatric subjects show that progressively localized brain activity is required, even after relatively brief periods of practice, to perform the gestures correctly. Our Aims are (1) to examine whether children with ASD require more practice to learn new gestures by imitation; (2) to determine whether children with ASD have less remodeling of brain networks associated with practice of the gestures; and (3) to assess whether these differences correlate with the cardinal symptoms of ASD: impairments of social and communicative skills. We hypothesize that children with ASD will indeed be less efficient at learning these new motor skills and that their brain networks will have less of an ability to change as a result of imitation-based practice. While there is extensive research into the fact that individuals with ASD have impairments in a range of skills, the proposed research is a critical step in understanding how altered skill learning-by imitation-may contribute to the abnormal development of these skills in the first place.